Laptop computers are designed to operate with both AC adapters and batteries as power sources but can properly function when receiving power from only one source. Dell says a laptop does not draw from the battery power at all when connected to an outlet via an AC adapter. The laptop will work just fine if the battery has been removed from the device, but it has to remain tethered to a power source through the AC adapter at all times to function.

Power without a Battery

Aging laptop batteries can lose their ability to hold a charge to the point where the battery is no longer able to power the laptop. The laptop can still be used with a dead battery through AC adapter power only because the laptop is designed to switch between power sources: it doesn't draw power from the battery when the AC adapter is in use. Bloomberg Business weekly says manufacturers are hesitant to endorse using a laptop without the battery because it leaves the charging terminals exposed on the bottom of the computer, making the sensitive part easier to damage.

The Battery is a Backup

A laptop's battery is actually the device's secondary power source: the AC adapter is the primary. PCWorld says battery usage is intended for times when AC power is not available. The battery is used to maintain power to the laptop in the event that the AC adapter power source is either unavailable or cut from the system. Unless the battery is being charged through an external charging device, the battery relies on the AC adapter connection to the computer to charge.

Normal Power Troubleshooting Process

Removing a laptop's battery and running the device from AC power only is a commonly used step in diagnosing a power problem with a laptop computer. PC Magazine writes that you can diagnose a battery problem by removing the battery and running the laptop on AC adapter power only. The problem is usually with the battery itself if the laptop works fine without the battery connected but has problems working when the battery is installed. CBS Moneywatch says that running a laptop on AC adapter power only is a way to confirm that the AC adapter is functioning.

Without Battery Disadvantages

Running a laptop without a battery leaves the device at high-risk of power loss. If you continually run the laptop from an AC adapter, you may opt to remove the battery during use to extend the battery's life for when you need it. Wired says that keeping a laptop plugged in all the time can shorten a battery's lifespan. However, running a laptop without a battery puts the device at a disadvantage: the device will force shut down instantly if the cord is unplugged or the power goes out. Laptop charger ports are notorious for breaking from wear-and-tear: the port may get to the point where wiggling the AC adapter cable makes the difference between full power and no power.